ImageAssetManager will casue crash when decode asset throw IOException

Littie v3.1.0 I have met some crash logs about Lottie recently. When I read the source code ,I find there maybe a bug. Class:com.airbnb.lottie.manager.ImageAssetManager

 InputStream is;
    try {
      if (TextUtils.isEmpty(imagesFolder)) {
        throw new IllegalStateException("You must set an images folder before loading an image." +
            " Set it with LottieComposition#setImagesFolder or LottieDrawable#setImagesFolder");
      }
      is = context.getAssets().open(imagesFolder + filename);
    } catch (IOException e) {
      Logger.warning("Unable to open asset.", e);
      return null;
    }
    bitmap = BitmapFactory.decodeStream(is, null, opts);
    bitmap = Utils.resizeBitmapIfNeeded(bitmap, asset.getWidth(), asset.getHeight());

When AssetManager open file throw IOException,this is is null,and this bitmap will be null.and Utils.resizeBitmapIfNeeded will throw NPE. I find the newest version alse has the problem, so please recheck these code,thanks!

[gpeal]

@1wayticket reopening to track this.

[1wayticket]

@gpeal Allright~